hi, the following code generates a compile error raising from a macro in /ublas/traits.hpp: BOOST_STATIC_ASSERT ((boost::is_same<T1, T2>::value)); Because I'm trying to prod on a vector of size_t and a matrix of unsigned char. Because I want to save memory (the matrix is really huge) and I know the value in m will never exceed 255. The expression is ok to me (of course the result value is size_t). But the ASSERT prevent me from doing this. Is there a workaround that permits me doing this kind of case without sacrificing the memory efficiency? Using size_t in the matrix will use three times more memory. ublas::vector<size_t> v1(5); matrix<unsigned char> m(5,5); prod(m,v1); the same problem arises when I do prod(m,v2); here v2 is a vector<double> -- Sincerely yours, Zhang Le